Combining Module Interfaces

Is there a way to combine interfaces into a single file?
If I have modules A and B, I want to create a module C with all the
exported definitions of A and B such that I can compile against C.hi file
without needing the A.hi and B.hi files.
I tried this:
module C (module A,module B) where
{
import A;
import B;
}
...but if I attempt to compile against C.hi using definitions from A and
B, GHC complains if I don't have A.hi and B.hi. I want C.hi to contain
everything that A.hi and B.hi do.
--
Ashley Yakeley, Seattle WA